A woman shot dead three people and injured three more before turning a gun on herself in an attack at a warehouse complex in Maryland, US police say.
The shooting happened on Thursday morning at a pharmacy distribution centre in Perryman, near Baltimore.
The attacker, Snochia Moseley, 26, died from a self-inflicted gunshot wound. The motive for her attack is unclear.
Mass shootings by women are rare, with more than 95% of such attacks in the US carried out by men.
The victims who died included Sunday Aguda, 45, Brindra Giri, 41, and Hayleen Reyes, 41, police said on Friday.
'Officers fired no shots'
The shooter was a temporary employee who reported for work as usual that morning, Harford County Sheriff's Office said.
But shortly after 09:00 local time (13:00 GMT) she began shooting outside, then inside the facility, with a 9mm Glock handgun that she had brought with her.
Police were on the scene within five minutes, by which time the shooter had killed three people and injured three more.
Officers found the suspect in a critical condition, with a self-inflicted gunshot wound to the head - she died later in hospital.
She was from Baltimore County, police said.
She legally owned and had registered the handgun, and had taken several magazines of ammunition with her, police said.
The sheriff's office initially urged residents to avoid the area, which is about 40km (25 miles) north-east of Baltimore, as hundreds of employees evacuated the facility and nearby buildings.
Shooter became 'increasingly agitated'
Investigators say the suspect was "suffering from a mental illness and over the last two weeks had become increasingly agitated".
They say she had been employed at the facility for less than two weeks before the attack.
She had no criminal arrest record, but had her car stopped three times in the area in just the past month.
The suspect was issued tickets for not having proper vehicle registration, among other infractions, according to the Baltimore Sun newspaper.
Authorities have described her as "disgruntled". A school friend told the newspaper that she was not an angry person but felt the "world was against her".